1. Field of the Invention
The present invention relates to a measurement chamber that permits an application of light for measuring a property of a sample, and more particularly, a measurement chamber with an optical window that permits an adjustment of the optical window while maintaining the integrity of the measurement chamber so that it can be used in spectroscopic measurements.
2. Description of Related Art
Numerous different instruments utilize an illumination of a sample with radiation, including light in the visible, ultraviolet and infrared ranges where the light interacts with the sample to provide a characteristic that can be appropriately measured to determine the properties of the sample. Various forms of spectroscopic measuring devices such as optical interferometers and ellipsometers position a test sample within a sample chamber having an optical window or windows that isolate the sample from exterior influences such as atmospheric pressure and temperatures.
FIG. 6 discloses a prior art schematic view of a conventional testing instrument with an optical window 66. A sample chamber 61 is usually maintained at a low pressure or vacuum state and/or at a low temperature, and the optical window 66 isolates its interior with the sample 63 from the exterior ambient conditions. Light 68 is disclosed as entering into the sample chamber 61 through the optical window 66 for interacting with the sample 63. The light 69 that has been influenced by the sample is also outputted via the optical window 66 to a detector not shown.
The angle of entrance and exit of the light 68 is inclined with regards to the optical window 66, and the measurement results cannot be performed for the same point on the sample 63 due to the influences of chromatic aberration.
In the case of performing a spectral ellipsometric measurement by using a low temperature cryostat, there is also a need for varying the angle of light entering into the sample chamber to define a measurement point on the surface of the sample. If the light enters at an angle as it transmits through an optical window, there is a potential problem in that the optical path or optical axis can be varied depending on the wave length because the optical window is fixed. As a result, errors in the measurement can be realized.